This invention relates to a network system for transmitting sales data including commercial scales capable of calculating purchase prices from measured weight data and unit prices or cash registers for registering and summing up purchase prices and a computer for carrying out production management, inventory management and customer management by analyzing purchase data, customer data and the like transmitted from such scales or cash registers.
Scales capable of calculating purchase prices from measured weight data and unit prices and of displaying them are commonly used at stores where meats and cooked foods are sold by their weights. Recently, there are stores having two or more of such scales connected together by communication cables such that a customer may make purchases from different scales but the data on his or her purchases are transmitted to all the scales in the store and the total purchase price can be calculated whenever the final purchase has been made and the customer is ready to pay. The technology of such a system of scales has been disclosed, for example, in Japanese Patent Publications Tokko 61-5606, 61-5607 and 61-18125.
Conventional systems as described above are inconvenient because communication cables must be provided and hence the scales which are connected to these cables cannot be moved around freely. Moreover, the cables can be quite unsightly since they must be extended to wherever the scales are disposed.
One of the methods of overcoming this problem has been to make use of wireless means for communicating data among the scales but this method has not been totally satisfactory from the point of view of reliability. Since the data to be communicated relate to purchase prices for the customers, the system must be able to transmit signals reliably.
Another method is to make use of a flexible memory-storing medium such as a magnetic card or an IC card for transmitting the sales data of customers from one scale to another. This method is superior to the one explained above from the point of view of reliability but the operation is disadvantageously troublesome because the card must be inserted into and removed from a reader-writer for each purchase data transmission. Where foods are handled, in particular, the user must be particularly careful in the handling of the card from the hygienical point of view.